EFFECTS OF PH ON THE PEROXIDATION OF HUMAN HIGH-DENSITY-LIPOPROTEINS (HDL) INITIATED BY O-2-CENTER-DOT-HO2-CENTER-DOT FREE-RADICALS GENERATED BY WATER RADIOLYSIS

A study of the radiation-induced peroxidation of high-density lipoprot eins (HDL) in neutral (pH 7.0) and slightly acidic (pH 5.7) oxygen-sat urated aqueous solutions is reported. The following markers of lipid p eroxidation have been quantitatively measured as a function of the abs orbed radiation dose: (a) the decrease of vitamin E concentration, (b) the formation of thiobarbituric acid-reactive substances (TBARS) and conjugated dienes, and (c) the appearance of differential fluorescence . Highest HDL oxidation yields are observed at pH 5.7. This result is in agreement with the known property of HO2. of being a more powerful oxidant than its conjugated base O-2(.-). The results obtained with HD L are compared and discussed with those already obtained for low-densi ty lipoproteins (LDL).